Characterising systems for respiratory therapy

Abstract

Apparatus and methods provide system characterisation such as for operation of respiratory treatment apparatus. Such a characterisation may include a determination of a patient interface type and/or an event such as a leak or blocked vent. For a characterisation, one or more controller(s) or processor(s) may be configured to make a determination of parameters that best fit a template curve, such as a quadratic function, to a plurality of measurements, such as data points. Each data point may include a pressure value, and a flow rate value at the pressure value. Parameters from the function may then be applied, such as with a data structure to characterize the system, such as with an identification of the patient interface type from the parameters. In some versions, parameter(s) of operation of the apparatus may be adjusted based on the characterisation, such as by using the parameters of the template.

The invention claimed is: 
     
         1 . Apparatus for respiratory therapy, the apparatus comprising:
 a pressure generator configured to generate a flow of air to a patient interface for a respiratory therapy for a patient;   a pressure transducer configured to generate a signal representing a pressure of the flow of air;   a flow rate transducer configured to generate a signal representing a flow rate of the flow of air;   a controller configured to:
 receive the pressure signal and the flow rate signal from the transducers; 
 analyse the pressure signal and the flow rate signal to identify the patient interface; and 
   a central controller of the pressure generator, the central controller configured to:
 receive the identification of the patient interface, and 
 control the pressure generator to adjust a property of the flow of air based on the identification, 
   wherein the analysis comprises a determination of parameters that best fit a template curve to a plurality of points, each point comprising: (a) a pressure value, and (b) a flow rate value at the pressure value.   
     
     
         2 . The apparatus of  claim 1 , wherein the controller is the central controller of the pressure generator. 
     
     
         3 . The apparatus of  claim 1 , wherein the controller is a processor of a remote external device in communication with the central controller of the pressure generator. 
     
     
         4 . The apparatus of  claim 1 , wherein the central controller is configured to determine the identification of the patient interface based on the determination of parameters. 
     
     
         5 . The apparatus of  claim 1 , wherein the central controller is configured to determine a control parameter for adjustment of the property of the flow of air. 
     
     
         6 . The apparatus of  claim 5 , wherein the central controller is configured to adjust the control parameter based on the determination of the parameters. 
     
     
         7 . The apparatus of  claim 1 , wherein the pressure value comprises a value of a low-pass filtered version of measured pressure from the pressure signal. 
     
     
         8 . The apparatus of  claim 7 , wherein the flow rate value comprises a mode of a histogram of values of measured flow rate from the flow rate signal at the pressure value. 
     
     
         9 . The apparatus of  claim 8 , wherein the controller is configured to determine the mode of the histogram of values, and wherein the histogram of values is a histogram of a low-pass filtered version of measured flow rate from the flow rate signal at the pressure value. 
     
     
         10 . The apparatus of  claim 1 , wherein the controller is configured to subtract a pressure drop from a measured pressure value from the pressure signal for the analysing. 
     
     
         11 . The apparatus of  claim 10 , wherein the pressure drop is a pressure drop of an air circuit connecting the apparatus to the patient interface at a measured flow rate from the flow rate signal. 
     
     
         12 . The apparatus of  claim 1 , wherein the controller is configured to determine the plurality of points during a therapy session comprising automatic positive airway pressure (APAP) therapy. 
     
     
         13 . The apparatus of  claim 1 , wherein the controller is configured to condition the analysis on checking of a time of therapy use and/or a range of provided therapy pressures of a therapy session. 
     
     
         14 . The apparatus of  claim 1 , wherein the controller is configured to estimate a leak flow rate from measured pressure from the pressure signal, measured flow rate from the flow rate signal, and the determined parameters. 
     
     
         15 . The apparatus of  claim 14  wherein the controller is configured to determine a bias flow rate based on a pressure-flow curve defined by the determined parameters. 
     
     
         16 . The apparatus of  claim 15  wherein the controller is configured to determine the leak flow estimate by subtracting the bias flow rate from the measured flow rate, wherein the measured flow rate comprises a total flow rate. 
     
     
         17 . The apparatus of  claim 15 , wherein the pressure-flow curve defined by the determined parameters comprises a quadratic function. 
     
     
         18 . The apparatus of  claim 15 , wherein the controller is configured to determine the bias flow rate by inverting the pressure-flow curve defined by the determined parameters. 
     
     
         19 . The apparatus of  claim 14 , wherein the controller is configured to estimate a respiratory flow rate of the patient from the measured flow rate, the measured pressure, the determined parameters, and the estimated leak flow rate. 
     
     
         20 . The apparatus of  claim 19 , wherein to control the adjustment to the property of the flow of air, the central controller is configured to:
 detect an event from the estimated respiratory flow rate of the patient, and   adjust a treatment pressure of the flow of air in response to the detected event.   
     
     
         21 . The apparatus of  claim 20 , wherein the event is an event from the group consisting of: an apnea, a hypopnea, a snore, and inspiratory flow limitation. 
     
     
         22 . The apparatus of  claim 1 , wherein the analysis further comprises:
 a comparison of the determined parameters with a plurality of sets of parameters in a database, and   the identification of the patient interface based on the comparison of the determined parameters.   
     
     
         23 . The apparatus of  claim 1 , wherein the template curve is a quadratic function. 
     
     
         24 . The apparatus of  claim 1 , wherein the controller is configured to determine a vent blocking event based on the determined parameters. 
     
     
         25 . The apparatus of  claim 24  wherein the controller is configured to determine the vent blocking event based on comparing a measure of average total flow rate with a flow rate at a given device pressure according to a function comprising the determined parameters. 
     
     
         26 . The apparatus of  claim 25  wherein the controller is configured to generate an indication of the vent blocking event if the measure of average total flow rate is less than the flow rate according to the function. 
     
     
         27 . A method of operating in a respiratory treatment apparatus that is configured to generate a flow of air to a patient interface for a respiratory therapy for a patient, the method comprising:
 accessing data representing a measured pressure of the flow of air, the measured pressure generated using a pressure transducer;   accessing data representing a measured flow rate of the flow of air, the measured flow rate generated using a flow rate transducer;   analysing, in a controller, the measured pressure and the measured flow rate to identify the patient interface,   wherein the analysing comprises determining parameters that best fit a template curve to a plurality of points, each point comprising: (a) a pressure value, and (b) a flow rate value at the pressure value; and   control adjusting a property of the flow of air based on the identification.   
     
     
         28 . The method of  claim 27  wherein the controller determines the identification of the patient interface based on the determining of parameters. 
     
     
         29 . The method of  claim 27 , further comprising controlling, in the controller, a determination of a value of a control parameter for operating a pressure generator of the respiratory treatment apparatus based on the identification of the patient interface. 
     
     
         30 . The method of  claim 27 , further comprising deriving the pressure value by low-pass filtering the measured pressure. 
     
     
         31 . The method of  claim 30 , further comprising determining the flow rate value by deriving a histogram of values of the measured flow rate at the pressure value and determining a mode of the histogram. 
     
     
         32 . The method of  claim 31 , wherein deriving the histogram comprises determining values of a low-pass filtered version of the measured flow rate at the pressure value. 
     
     
         33 . The method of  claim 27 , further comprising subtracting a pressure drop value from the measured pressure for the analysing. 
     
     
         34 . The method of  claim 33 , wherein the pressure drop value represents a pressure drop of an air circuit connecting the respiratory treatment apparatus to the patient interface at the measured flow rate. 
     
     
         35 . The method of  claim 27 , wherein the controller determines values for the plurality of points with data from a therapy session comprising automatic positive airway pressure (APAP) therapy. 
     
     
         36 . The method of  claim 27 , further comprising conditioning the analysis on checking of a time of therapy use and/or a range of provided therapy pressures of a therapy session. 
     
     
         37 . The method of  claim 27 , further comprising estimating a leak flow rate from the measured pressure, the measured flow rate, and the determined parameters. 
     
     
         38 . The method of  claim 37  further comprising determining a bias flow rate based on a pressure-flow curve defined by the determined parameters. 
     
     
         39 . The method of  claim 38  wherein determining the leak flow estimate comprises subtracting the bias flow rate from the measured flow rate, wherein the measured flow rate comprises a total flow rate. 
     
     
         40 . The method of  claim 38 , wherein the pressure-flow curve defined by the determined parameters comprises a quadratic function. 
     
     
         41 . The method of  claim 38 , further comprising determining the bias flow rate by inverting the pressure-flow curve defined by the determined parameters. 
     
     
         42 . The method of  claim 37 , further comprising estimating a respiratory flow rate of the patient from the measured flow rate, the measured pressure, the determined parameters, and the estimated leak flow rate. 
     
     
         43 . The method of  claim 42 , further comprising:
 detecting an event from the estimated respiratory flow rate of the patient, and   adjusting a treatment pressure of the flow of air in response to the detected event.   
     
     
         44 . The method of  claim 43 , wherein the event is an event from the group consisting of: an apnea, a hypopnea, a snore, and inspiratory flow limitation. 
     
     
         45 . The method of  claim 27 , wherein the analysing further comprises:
 comparing the determined parameters to a plurality of sets of parameters in a database, and   identifying the patient interface based on the determined parameters.   
     
     
         46 . The method of  claim 27 , wherein the template curve is a quadratic function. 
     
     
         47 . The method of  claim 27 , further comprising determining a vent blocking event based on the determined parameters. 
     
     
         48 . The method of  claim 47  wherein the determining the vent blocking event comprises comparing a measure of average total flow rate with a flow rate at a given device pressure according to a function comprising the determined parameters. 
     
     
         49 . The method of  claim 48  generating an indication of the vent blocking event if the measure of average total flow rate is less than the flow rate according to the function. 
     
     
         50 . A non-transitory processor readable medium configured with program instructions for controlling one or more processors to execute a method of operating a respiratory treatment apparatus, the method comprising the method of  claim 27 . 
     
     
         51 . Respiratory treatment apparatus comprising:
 a pressure generator configured to generate a flow of air to a patient interface for a respiratory therapy for a patient;   a pressure transducer configured to generate a signal representing a pressure of the flow of air;   a flow rate transducer configured to generate a signal representing a flow rate of the flow of air; and   a controller comprising one or more processors with the non-transitory processor readable medium of  claim 50 .   
     
     
         52 . A system for controlling a respiratory therapy, comprising:
 means for supplying a flow of air to a patient interface as a respiratory therapy;   means for generating a flow rate signal representing a flow rate of the flow of air;   means for generating a pressure signal representing a pressure of the flow of air;   means for analysing the flow rate signal and the pressure signal to identify the patient interface; and means for adjusting a property of the flow of air based on the identified patient interface,   wherein the analysing comprises determining of parameters that best fit a template curve to a plurality of points, each point comprising: (a) a pressure value, and (b) a flow rate value at the pressure value.